noun
1
BAD : He was determined to get the money by all means.
GOOD : He was determined to get the money by whatever means.
BAD : They intend to become famous by all means, even if they have to risk their lives.
GOOD : They intend to become famous by whatever means, even if they have to risk their lives.
◆◆◆
By all means (= certainly) is used in formal spoken English to show that you are happy to accept someone's request or suggestion: 'Would you mind if I stayed a bit longer?' 'By all means.'
When you mean 'by using any method, even if it is unkind or illegal', use by any means or by whatever means (are available/necessary) : 'They are determined to get their hands on the property by whatever means are necessary.'
2
BAD : Learning English is a means to improve one's career prospects.
GOOD : Learning English is a means of improving one's career prospects.
◆◆◆
means of (doing) sth = a way or method: 'It's time we stopped using force as a means of settling disputes.' 'There must be an easier means of gaining their confidence.'
means to do sth (or means of doing sth ) = the thing that is required or necessary (to make something possible): 'These people have lost the means to support their families.' 'They would like to stop the war but lack the means to do so.'
3
BAD : By no means I want to suggest that people like being unemployed.
GOOD : By no means do I want to suggest that people like being unemployed.